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Re: filmscanners: Scanner resolution (was: BWP seeks scanner)
In a message dated 6/15/01 11:53:29 AM Eastern Daylight Time,
<< This implies to me that the film itself is the limiting factor for "image
sharpness". While we might all like to see 8000 ppi scanners for a number of
reasons, we won't actually resolve much more image content that the current
4000 ppi models are providing.
After all, 4000 ppi gives a resolution of 75 lp/mm or so, and it takes
pretty remarkable technique to actually get that kind of resolution onto
film. Or is my crude first-approximation assessment incorrect, and we
actually can't resolve detail in the scan at more than half that - say 40
lp/mm with reasonable contrast? Even that level is still sufficient for
prints that appear "sharp" at normal viewing distances.
Whatever the final outcome may be (once we've worked through the morass of
differences between film and digital image reproduction technology and
information theory) I'm still left with the feeling that current scanner
resolution is getting off the film most of what's actually there. An
order-of-magnitude improvement is probably not available in this system.
Paul Chefurka >>
Here is an interesting observation from Michael J. McNamara (PopPhotgraphy
July, p58)at the conclusion of the article on their scanner tests: "...Even
the best 4000 dpi scanners we've tested aren't capable of capturing all the
detail found in a 35mm color original under optimum conditions (tripod,
mirror lockup,etc). In our tests the highest res we've found in a 35mm color
slide or negative is 77 lp/mm. The best 4000 ppi scanner can capture about
60 lp/mm, about 25% lower. But that's perfect, because under normal shooting
conditions (i.e., handheld instead of tripod mounted), 60 lp/mm is about all
you'll ever get from an SLR."
Whatever the theoretical merits of McNamara's observations, it appears to me
that they clearly are in agreement with the conclusions by Paul and Raphael.
BTW, the 2900 ppi Nikon CoolscanIV resolved 53.3 lp/mm vs 60 lp/mm for the
CoolScan 4000ED; does this imply that it "outperformed" the more expensive
scanner on a relative basis?